Remove the trunk panels to access the ML amp to get the input for the new sub amp.
Access the ML amp to get to the speaker wiring. This was the most difficult part because of the area restrictions. Remove the bolts (3) that hold the two cross braces above the amp. I then just pushed the braces up and over bending them slightly out of the way. I think you could remove them if you can access them from behind the back seat. The bolt holding the amp in are then easily accessable with a 12-16" extension w/ 10 mm socket. There is enough play in the cables to lift the amp up and out without disconnecting. If you do disconnect the amp, remember to initialize the system again after replacement.
This is done by putting the key on "ACC" for 5 minutes so the amp can boot and read the system settings. After 5 minutes tune ingition off for 1 min, then turn back to ACC or ON and power the system on.
Since the head unit uses a balanced output I decided to go with a line out converter to the front L and R mid/sub speakers for the new sub amp. The wiring is as follows for the front woofer outputs:
white w/ black stripe - ground
gray 12+ volt acc line for sub amp
You can see that I initially tried to get signal to the amp using the sub outputs. That's the two connectors to the blue w/ red and red w/ blue connections with the black splice wires. The sound output was no good so decided to go with the line out conversion.
Everything is all wired and finished with the amp in place. I used a MA Audio unit with bridged output to the sub.
All I can say is that the sound is awesome and far superior to the factory setup.